Method of triggering at least one airbag in a vehicle

Abstract

A method of triggering at least one airbag in a vehicle is described, in which two or more criteria are used in the decision to fire the second stage of a two-stage airbag. Variables derived from measurement signals of an acceleration sensor are used as criteria. If these variables exceed threshold values within pre-defined times a firing decision is brought about. The criteria are chosen depending on the type of vehicle. Characteristic curves are used as threshold values. These characteristic curves may be modified depending on the use of a belt.

1. A method of triggering at least one airbag in a vehicle in at least two stages, comprising:
 detecting an acceleration of the vehicle using at least one acceleration sensor of an airbag controller located centrally in the vehicle; 
 deriving at least two criteria from the at least one acceleration sensor, wherein the at least two criteria are selected depending on a type of vehicle; and 
 triggering a second stage of the at least one airbag as a function of relationship between the at least two criteria; 
 wherein the second stage is triggered if each of the at least two criteria exceeds pre-defined threshold values within respective pre-defined times, and wherein the second stage is fired after a residual firing time if at least one of the at least two criteria does not reach the respective threshold value in the respective pre-defined time. 
 
   
   
     2. The method according to  claim 1 , further comprising: selecting the at least two criteria from the following parameters:
 an acceleration in a direction of travel, 
 an aggregate acceleration in the direction of travel, 
 an integrated absolute value of the acceleration in the direction of travel, 
 an integrated acceleration in the direction of travel in a pre-defined time window, 
 an acceleration transverse to the direction of travel, 
 an aggregate acceleration transverse to the direction of travel, 
 a sum of the integrated acceleration in and transverse to the direction of travel, 
 a double integrated acceleration transverse to the direction of travel, and 
 an acceleration determined at an angle to the direction of travel. 
 
   
   
     3. The method according to  claim 1 , further comprising:
 pre-defining a minimum delay time for the firing of the second stage. 
 
   
   
     4. The method according to  claim 1 , further comprising:
 using respective time-dependent characteristic curves to determine the pre-defined threshold values. 
 
   
   
     5. The method according to  claim 1 , further comprising:
 recognizing that the respective threshold value has been exceeded by the respective criterion if the respective criterion is above the respective threshold value for a pre-defined decision time. 
 
   
   
     6. The method according to  claim 3 , wherein the second stage is fired after the minimum delay time if the first stage is triggered within a pre-defined accident severity time. 
   
   
     7. The method according to  claim 4 , further comprising:
 modifying the characteristic curves depending on whether a seat belt is being used.